Thanks fishy68.
The noise is not coming from the rear differential. It sounds like it's coming from the rear half of the transmission.
I have had the rear on stands and the rear diff is behaving normally.
The whirring sound when being towed is less noisy than when the engine is running. When it's being towed it sounds more like a ratchet than a whirring.
if you get a ratchet spanner and grab it by the socket and let the handle spin around and round, it sounds kinda like that when being towed.
Like one perpetual barrage of clicks that sound almost constant.
you have to listen for it but it's unmistakably there. especially if it picks a little bit of speed up (like 5MPH)
When it's running I can't really hear the engine much, mostly the whirring drowns it out. the exhaust is a twin 2" system with front and rear mufflers.
Whatever is making the whirring sound is putting enough load on the engine to make it stall at idle in any gear except reverse (including park and neutral).
I have very little knowledge on torqueflites but to my knowledge this one is not one able to be roll started. So I think that means it doesn't have a rear pump.
I know it's not ideal to swap another trans back in before diagnosing the problem on this one.
however there's no way I'm giving my car to the transmission shop with an engine that's not run in yet.
it only ran for 25-30 minutes and has never even had any load on it yet.
Would it help if I took a video of the car's symptoms? Whirring etc.
